There are many well-known methods of mounting electronic components to a substrate. One method is the conventional "reflow soldering" process used for attaching terminations of surface mount components. In the conventional reflow soldering process the terminations of the surface mount components have a thin pre-tin solder coating and are attached during a manufacturing process to rectangular mounting pads etched onto a substrate. The process comprises printing a solder paste through a stencil having apertures matching the size and location of the mounting pads, placing the surface mount component terminations on top of the solder paste in alignment with the mounting pads therefor, and passing the substrate and surface mount components through a reflow solder oven for heating the pre-tin solder coating and solder paste to a liquefied state to attach the terminations to the mounting pads.
Disadvantageously, during the conventional reflow soldering process, termination attachment defects occur because the terminations of the surface mount components do not always remain aligned with the mounting pads. Errors in initial placement of the surface mount components, vibrations from equipment used to move the substrate through a manufacturing area, and general handling also can cause misalignment. Unfortunately, the mounting pads used in the conventional process are only partially effective in correcting any misalignment that occurs.
The trend of electronic devices, such as selective call receivers, towards smaller sizes requiring micro-miniature components tends to increase defect rates even further in the conventional reflow soldering process. This is because the defect rate due to misalignment increases as the terminations, mounting pads, and alignment tolerances become more critical.
Thus, what is needed is a better way of mounting surface mount components to corresponding mounting pads on a substrate. A method and apparatus that can minimize component misalignment and reduce attachment defects on microminiature components is highly desired.